WSO Water Treatment Grade 1 Practice Test 2026 - Free Water Treatment Practice Questions and Study Guide

An artesian aquifer is characterized by water that is trapped under pressure between layers of impermeable rock or sediment. When a well is drilled into a confined aquifer, the pressure from the water may cause it to rise spontaneously to the surface without the need for pumping. This phenomenon occurs because the water in a confined aquifer is under higher pressure than the atmospheric pressure.

In contrast, an unconfined aquifer has a water table that is free to rise and fall, and water can seep in from the surface, where the pressure is equal to atmospheric pressure. A surface aquifer generally refers to water bodies like rivers or lakes, which are not confined or under pressure in the way an artesian aquifer is. A permeable aquifer simply refers to an aquifer that has the ability to transmit water easily, but does not inherently imply the conditions necessary for artesian flow.

Thus, the specific characteristics of a confined aquifer are what allow artesian conditions to develop, making it the only correct choice for where an artesian aquifer could occur.